This invention relates to poly(aryl ether ketones) and in particular to copolymeric poly(aryl ether ketones).
Poly(arylene ketones), in particular, all para-linked poly(aryl ether ketones), possess many desirable properties, for example, high temperature stability, mechanical strength, and resistance towards common solvents. The preparation of poly(aryl ether ketones) by two different approaches has been described in the literature. The first approach is an electrophilic synthesis in which an aryl ketone linkage is formed. The second is a nucleophilic synthesis in which an aryl ether linkage is formed.
Efforts in recent years have been directed to the development of economical processes for commercial manufacture of these polymers. One factor considered in the economics is the cost of the monomer(s) used in preparing the polymer. One economically attractive polymer is described in U.S. Pat. No. 3,065,205 to Bonner and is produced from diphenyl ether and terephthaloyl chloride. The resulting polymer contains all para-linkages but is reported in U.S. Pat. No. 3,516,966 to Berr to be non-melt processable and subject to degradation under melt processing conditions. The problem is avoided by Berr by the use of a mixture of terephthaloyl and isophthaloyl chloride together with diphenyl ether.
It has been found that preparation of the all paralinked polymer derived from diphenyl ether and terephthaloyl chloride by the electrophilic process described by Bonner and Berr results in a polymer of relatively low molecular weight. A further disadvantage of the polymer is addressed in U.S. Pat. No. 3,767,620 to Angelo et al. Polymers prepared from diphenyl ether and terephthaloyl chloride or mixtures of tere- and isophthaloyl chlorides are reported to contain xanthydrol end groups which tend to make the polymer melt unstable. Angelo's solution to the problem is to react the polymer with a reducing agent. While such reduction may improve melt stability to a certain extent, the reduced end groups are likely to undergo air oxidation at elevated temperatures due to the presence of tertiary benzylic hydrogen atoms.
We have now discovered that high molecular weight, commercially viable, melt processable polymer can be prepared from diphenyl ether and terephthaloyl chloride by the addition of an appropriate comonomer. The resulting copolymer has higher molecular weight, lower xanthydrol end group content and improved melt stability over the polymer prepared from diphenyl ether and terephthaloyl chloride.